The invention relates to a device for producing and delivering of stacks of plastic bags, particularly bags for automated machines, with a crosscut-welding station for making welding seams in a double-layer foil web of plastic material and separating the plastic bags from the web of plastic material, optionally with a stamping station for producing stacking holes and an interlocking station, as well as a pin stacking conveyor with a stepwise movable pin stacking chain and a discharge station which has a robot with a grip hand.
One problem with all bag-producing machines with a subsequently arranged collection and stacking device consists in that the output of the stacking, respectively collection device has to be adjusted to the continuously working bag fusion machine so that no interruption of the cycle occurs, while a finished bag is removed from the stacking station and an empty stacking mechanism is introduced in the stacking station. In the production of the bag stacks it is known to fix the same by means of wire brackets. For this purpose either the bag stack is lifted from the stacking pins of the pin stacking conveyor and with the now loosely superimposed bags pushed over the legs of the wire brackets, or the legs of the wire brackets are inserted in slot-like recesses of the stacking pins of the pin stacking device, removing the bag stacks this way. Subsequently the bag stack has to be secured by safety plates, respectively rubber stoppers arranged on the bracket legs. Sometimes the separate bag stacks are covered on both sides with paper strips, respectively intermediate paper layers. The manual removal of the bag stacks and the insertion of the wire brackets represents a comparatively big physical effort for the operator, since the same, repetitive motions have to be performed in a very short time, because of the relatively high production speed.
To the extent that the use of wire brackets for holding the individual bags in the bag stack should be eliminated, an interlocking of the individual plastic bags to a bag stack can already be achieved in the pin stacking conveyor, in that the bags are fused together by heat in defined locations, for instance in an area defined by perforations. This way a considerable simplification in the production of the plastic bags is reached, since the removal of the bag stacks from the pin stacking conveyor can be performed much easier and finally also the packaging of the bags in cardboard boxes or the like is also simplified. However it still remains the obligation of the operator to examine the quality of the bag packages and to prepare them for packaging for instance in cardboard boxes.
From DE 38 34 115 can be seen that the concept of an automated removal process in the removal station by means of a robot is not new. However in the end at that time it was considered much too complicated and expensive to be put to use.
Indeed from EP 0 384 281 A1 a device for stacking bags on wire brackets has been known, whereby the stacking device has stepwise movable stacking plates, onto which the bags can be stacked by means of wire brackets. The positioning of the wire brackets on the stacking plates is done by means of an automatically controlled and driven robot with a grip hand. An obvious additionally arranged robot with grip hand can furthermore remove from the stacking plate the stacks interlocked by wire brackets and rubber stoppers and depose them on a transport belt.
It is the object of the invention to create a device of the mentioned kind suitable for producing and delivering stacks of plastic bags, particularly bags for automated machines, which further simplifies the and accelerates especially the removal and transfer of the bag stacks, so that an operator can limit his function only to the remaining quality control of the bag stack at an easily accessible location of the machine.
According to the invention this object is achieved in that the robot, which can be controlled in accordance with the relative motion of the pin stacking chain of the pin stacking conveyor, is equipped with a multifunctional program-controlled hand, and is positioned at the end of the pin stacking conveyor in such a manner that basically all the handling and motion operations required for the formation and delivery of the bag stacks can be performed. Thereby it is important for the stationarily mounted robot that the relative motion of the pin stacking chain be overlapped in longitudinal direction, and for the compensation of web vibrations also in transverse direction. With the means of the invention it is insured that the operator has only to take care of quality control, after which the finished bag packages can be packaged by the robot in for instance a cardboard box. Since the entire process of stack formation and delivery is performed by a single robot, the motions performed by the robot can be easily monitored by an operator, so that even at high production speeds, one operatorxe2x80x94depending on the type of bagxe2x80x94can also service, respectively supervise several machines under certain conditions.
This applies especially when the robot is substantially centrally located with respect to the longitudinal extent of the pin stacking conveyor and/or the robot is stationarily mounted in a support frame arranged behind the pin stacking conveyor above the circulation plane of the pin stacking chain. Preferably the support frame can also be designed for receiving the auxiliary means for the stack formation, such as wire brackets, safety plates, intermediate paper layers or the like and/or rotatably driven bracket supply device and/or a unit having a locking and correcting function.
All the devices required for the bag stack formation and delivery can be simply and safely fastened to the multifunctional hand, which has a first clamping bar and a second clamping bar adjustable in relation to the first, when the multifunctional hand has a mounting plate made of sandwich aluminum and a crossbeam adjustably guided in guide bars fastened to the mounting plates, which at the same time is designed to be the support of the upper clamping bar. Furthermore the mounting plate can be used for the mounting of auxiliary devices, such as holding device working with negative pressure for the safety plates, as well as intermediate paper layers and the like. Thereby the holding device for the safety plates can be designed as a suction :head and the holding device for the intermediate paper layers can be designed as a suction funnel.
For special purposes on the frontal side of the multifunctional hand wire bracket holders can be provided, by means of which wire brackets with bag packages are supplied to several machines arranged in a sequence on a common transport delivery belt, preferably designed as an elevated transport chain. In this case the brackets can be picked up from a bracket magazine by means of a straightening and feeding tong and transferred to the multifunctional hand of the robot.
To the extent that an interlocking of the bags by means of wire brackets and safety plates can be dispensed with, by means of the robot-controlled multifunctional hand, mounted according to the invention, it is possible to remove bag stacks interlocked through fusion from the pin stacking conveyor and to deliver them to a cardboard box or the like within a boxing station.
A further embodiment of the invention provides a collection device with a driving belt driven in a timed revolving manner which is arranged in the discharge station within the motion range of the robot, on which spaced-apart stacking plates each with a holding elements are fastened. Suitably it is further provided that the driving belt be guided about guide rollers which preferably arranged at a right angle to each other, at least one of the rollers being rotatably driven, and that further on the side facing the pin stacking conveyor, a filling station and on frontal side substantially transversely thereto a control and/or service station, as well as removal station on the side opposite to the driving belt are arranged.
The servicing is further simplified due to the fact that the stacking plates are fastened in an uneven number on the driving belt designed as a revolving chain and the latter are movable in a double timed step along the individual stations. In concrete execution a preparation of the stacking plates takes place starting from a bag stack receiving position in the filling station in a single timed step in a following start position, whereby in the holding element of the stacking plate a wire bracket, as well as optionally an inner intermediate layer, for instance in the form of a paper strip or a cardboard sheet, can be suspended in the wire bracket.
Further in a finishing position following the start position, which can also serve for control, optionally an outer intermediary layer and a rubber stopper or the like are slipped onto the legs of the wire bracket, The intermediate layers, as well as the rubber stoppers can be applied manually or in a suitable automated manner by the robot.
This way alternately a prepared stacking plate and a finished stacking plate are moved in a double timed step by means of the revolving chain into a bag stack removal position assigned to the removal station, whereby each time the finished bag stack can be seized by the grip arm of the robot which removes the bag stacks from the pin stacking conveyor and can be deposited in a packaging unit.